I assume that part of the real deal here is that British Airways gains access to some more slots at LHR, either directly though additional BA flights code-shared as LX flights as well, or actual LX flights now code-shared as BA flights. The Financial Times says that British Airways actually paid cash for the slots, though the press statement quoted by the previous poster has this statement : "In addition to this, British Airways, its new alliance partner, has agreed to provide a guarantee for CHF 50 million, secured against slots at London Heathrow."
So, I am just wondering what the actual position might be.
I can understand that if British Airways provides a guarantee for something, they can exercise title to the slots (and the revenue they obviously bring) if their guarantee is called for any reason. But I am unclear what the primary purpose of the guarantee is - in other words, who are British Airways guaranteeing.
Another possibility is that British Airways have indeed given or lent Swiss the CHF 50m, and their repayment comes from a lien on the revenue from the flights in question flown in those slots.